Windmills which are already known exist in various sizes and employ airfoil blades to drive an electric power generator through speed increasing gears. Those windmills are also arranged to feather the blades or to provide some energy absorbing means to drive the electric generator at or near a constant speed. Because it is not economical to provide a generator which is large enough to use the output of the windmill at high wind velocities which only rarely exist, and because the electric generator must be driven at a constant speed, the power of the high wind velocities is wasted. Also, windmill generating sets generate power only when the wind is available.
The object of the present invention is to provide a windmill which is less expensive to build and to maintain, compared to those heretofore known, and which is capable of converting the high wind velocities to usable energy.
Another object of this invention is to provide a windmill which includes means for storing the energy so that, for instance, the energy obtained during high wind velocities is available for use when there is no wind.
Another object of this invention is to provide a windmill energy converting system wherein energy of winds down to a low velocity can be converted to energy, such as by driving a centrifugal pump or an elastic fluid compressor, either of which requires input power in proportion to the cube of rotational speed, the same proportion in which power is developed by a windmill having non-feathering air foil blades, with rotational speed proportional to the wind velocity. In this instance, the converted energy is in turn converted to heat by restrictions to flow of the fluid, achieving this by having the windmill drive a blower which circulates air through a heat storage tank wherein the storage material can be a solid, such as brick. In accomplishing this object, heat can be generated for any of the purposes now commonly supplied by fossil fuel, and the heat can be supplied both when the wind is blowing and when there is no wind.
Further, windmills of all diameters can be of a similar design. A support is included in the construction and is rotatable relative to the direction of the wind and carries the air foil blades which are therefore directed. Controls are provided and adequately located so that there will be a reduction in the otherwise irregularities in air velocity to the rotating blades so that the blades will not be damaged by fatigue.
With the structure of this invention, where the unit is used for heating a residence, of say 1,200 square feet, there can be enough storage of heat to maintain a comfortable living temperature within the house for three to five days in zero outdoor temperature weather conditions without addition of heat from the wind.
Further, there can be a steam generating system operated by the windmill and it can be used both for heating and cooling of buildings, according to the arrangements of this invention. Still further, there can be a steam turbine operated by the steam produced from the windmill of this invention. A gas turbine can be operated on the intake or suction side of a compressor which is in the system, and the turbine can operate a generator and an objective is to have a reliable and economic system.
Existing large windmills usually drive generators connected to and supplementing established power sources at constant speed. Existing small windmills drive DC or AC generators at variable speed. Few references are made to windmills, driving pumps or compressors. Among these, U.S. Pat. No. 2,539,862 and U.S. Pat. No. 3,806,733, describe windmills conncted by gears to drive both positive displacement pumps and centrifugal compressors. In each case the pump or compressor must deliver fluid against a pressure higher than suction to drive a prime mover and, thru it, a generator or other mechanical output, or it must force the fluid into a storage vessel.
A positive displacement pump with pressure difference across it requires starting torque proportional to the pressure across it plus friction of the pump. An efficient windmill with one to three airfoil blades, develops low starting torque and cannot be designed to start and efficiently drive a positive displacement pump.
The piping connections of a centrifugal pump delivering fluid at a pressure higher than suction, must include a check valve to prevent flow back thru the pump when it is stationary or running below operating speed. A windmill and gear set designed to operate such a pump at a normal operating speed, will be lightly loaded from low wind velocity to a wind velocity corresponding to the pump speed at which fluid is discharged. Both the pump output and system efficiency are zero in this range of wind velocities. The wind will flow over the blade sections at low angles of attack and rotational speed of the windmill will be higher than that at which maximum power is recovered from the wind. When the pump is driven at speeds within its operating range, delivering fluid against substantially constant pressure, driving torque will increase rapidly with respect to speed.
This invention describes an air brake enclosed in an insulated housing to contain the heat resulting from absorption of energy by the brake and with provision to deliver the heat generated to storage or to use. A centrifugal impeller moves gas thru a short path of constant dimensions. Power required to rotate the shaft is proportional to the cube of rotational speed. When the brake is driven by a windmill thru a speed increaser of ratio required to match the windmill to the brake, the windmill will rotate at those speeds proportional to wind velocity within a safe operating range. The windmill will recover maximum energy from these winds.
This application of a centrifugal impeller in an enclosure within which it moves fluid thru a path of fixed geometry, results in a smooth curve of torque-speed relation. It cannot be compared to a pump in which fluid must be discharged against a fixed heat in which applications the curve of torque versus speed is discontinuous.
Mechanical energy recovered from wind and converted to heat is as effective in conserving fossil fuel as is the generation of electricity. The windmill of this invention is loaded by a brake which converts the mechanical energy directly to heat. It will cost less and will convert more of the energy of available winds in any geographic location to heat than a comparable windmill driving a generator. This windmill will require less maintenance and will last longer. Heat can be generated by the direct conversion of mechanical energy at a temperature limited only by the strength of the materials used to construct the brake. Storage of heat in rock has become recognized practice for heat recovered directly from solar radiation. Heat recovered from the wind either thru a generator or by direct conversion can be at higher temperature than direct solar heat and more can be stored in a given volume. Heat stored at high temperature can be converted to steam for distribution, can efficiently energize an absorption cooling system, heat service water and cook as appliances become available. A thermoelectric generator can supply electricity from stored heat upon demand without loss, if the air cooling the generator is used to heat a home.
A pneumatic transmission, equivalent in principal to the brake, capable of driving a generator at constant speed will be economical as a load for large windmills. Loss in the transmission and energy which the windmill can recover in excess of that required to drive a generator of economic rating, will be converted to heat. Thus windmills of all diameters according to this invention will economically recover the energy of winds to a higher operating velocity than equivalent windmills driving generators.